JPH09500354A - Superconductor with high Tc formed by metal heterostructure at atomic limit - Google Patents

Abstract

(57) [Summary] A superconductor with a high critical temperature formed by a heterostructure at the atomic limit that can be artificially achieved by molecular beam epitaxy, sputtering, lithography, chemical synthesis, electrochemical deposition or other similar techniques. At least a plurality of first portions of the superconducting metallic material forming a lattice of substantially equal elements having a constant period λ _p in at least a first direction (y) and a separation between the first portions. And a plurality of second portions formed of a substance having an electronic structure different from that of the first portion inserted in the first portion, and the heterostructure has a structure in which the plurality of first portions are electrons having a Fermi level. have a size (L) and the period (lambda _p) so as to satisfy the shape resonance condition for, and said plurality of second portions, the superconducting Pipadoko of superconducting material forming said first portion Critical temperature high superconductor characterized by having a Reference length xi] ₀ degree or smaller than (W).

Description

Description: High Tc superconductor formed by a metal heterostructure at the atomic limit Field of the invention The present invention is made with a first part of a size L superconducting material pushed towards the atomic limit. A superconductor having a high critical temperature, which is characterized in that it is formed by a heterostructure. Furthermore, the invention relates to a method for realizing these superconductors. DESCRIPTION OF THE PRIOR ART As is well known, commercially available superconducting metals exhibit only a very low critical temperature, which limits the industrial application of superconductivity. The onset temperature of zero, that is, the zero resistivity and the onset temperature of diamagnetism). These very low temperatures, on the order of a few degrees Kelvin, are unattainable without the use of cryogenic techniques, which means they are costly and difficult to operate. Therefore, research in this field is directed towards the realization of new superconducting materials with high critical temperatures. A recent innovation in this field is the discovery of superconductivity in cuprate perovskite, which exhibits a critical temperature on the order of 100 degrees Kelvin. However, ceramic superconductors of this type are fragile, difficult to shape, and difficult to keep oxygen content under control, which limits their industrial application. These challenges limit the industrial application of superconducting electronic devices using these ceramic materials. Another challenge to advances in this field is the lack of theory to explain superconductivity at high temperatures in these materials, and thus the inability to drive advances in these materials by experimental techniques. SUMMARY OF THE INVENTION The invention disclosed herein overcomes the above challenges by defining the physical parameters for designing a novel superconducting heterostructure with a critical temperature that is several times greater than the bulk metal superconducting material. It is to overcome. According to the invention, a plurality of first portions of superconducting material forming a lattice of substantially equal elements having a constant period λ _p in at least a first direction y, and not the same as these first portions. A plurality of second portions formed of a material, the plurality of first portions having a size L and a period λ _p measured in the first direction y, of the electrons at the Fermi level. The condition of “shape resonance” is satisfied, and the plurality of second portions have a size W of a degree of superconducting Pip pard coherence length ξ ₀ of the superconducting material forming the plurality of first portions. There is provided a superconductor having a high critical temperature characterized by having (W ≦ ξ ₀ ). The present invention is based on the discovery that high critical temperature superconductivity is associated with a particular heterostructure of a superconducting material, which heterostructure can be found in a cuprate perovskite. This dissimilar structure determines the "amplification degree" at the critical temperature compared to the same kind of superconducting material. Therefore, by forming an artificial dissimilar structure containing a superconducting metal with a low critical temperature, it is multiplied by the "amplification factor" associated with the selected heterostructure, and more so than with homogeneous materials. A superconductor having an artificially arranged dissimilar structure having a critical temperature several times higher, that is, 5 or 10 times higher, is formed. The invention also relates to a method for realizing a superconducting heterostructure with a high critical temperature, based on the main claims characterized by: -Providing a substrate made of a metallic or non-metallic substance. Forming a plurality of first portions of superconducting material on the substrate, the first portions having a selected dimension L and a selected spacing W in at least the direction y; Forming on said first part a second part of a material having a different electronic structure which acts as a spacer. The spacing W must be of the order of the superconducting Pippard coherence length ξ ₀ of the superconducting material forming the plurality of first portions (W ≦ ξ ₀ ). Repeating the above forming steps a selected number of times until a three-dimensional heterostructure is realized. The dimension L and the spacing W are selected to achieve a "shape resonance" state for electrons in the Fermi level of superconducting metals. In particular, the heterostructure can be realized by molecular beam epitaxy. A second method, which is simpler to achieve a higher critical temperature superconductor according to the main claim, is that a plurality of films of superconducting material, i.e. the first part, are provided with a plurality of non-superconducting films (or critical films). A superconductor having a low temperature), that is, a three-dimensional heterostructure made of those separated by a second portion, wherein the thickness L of the superconducting film and the thickness W of the non-superconducting film are It relates to the formation of a three-dimensional heterostructure that realizes a "shape resonance" state for electrons at the Fermi level in the lattice. In order to realize the "shape resonance" state, the thickness of the superconducting metal film is about the thickness of a few atomic layers, and therefore the film thickness must be controlled to be uniform at the atomic limit. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows the structure of a CuO ₂ plane in _{Bi 2} Sr ₂ CaCu ₂ O ~8 decorated by stripes of different Cu site conformations is a square pyramid distorted defined by the applicant It is a figure. FIG. 2 is a superconducting heterostructure at the atomic limit formed by a quantum fringe superlattice realized in Bi ₂ Sr ₂ CaCu ₂ O _˜8 , according to the present invention, with a critical superconducting temperature of about 5 by a factor of about 5. FIG. 3 shows a structure that gives amplification. FIG. 3 is a diagram showing the low-quality behavior of the quantum fringe superlattice in the CuO ₂ plane, in which the Fermi energy is tuned to the maximum value of the state density in order to raise the critical temperature. is there. 4 to 7 are diagrams showing several types of superconducting heterostructures at the atomic limit formed by superlattices of quantum wells, quantum wires, quantum dots, and quantum spheres. FIG. 8 is a diagram showing, as an example, a method of forming a superlattice of quantum wires. BEST MODE FOR CARRYING OUT THE INVENTION The present invention shapes a superconducting material into a plurality of units forming a superlattice, the size L of each unit being a function of the quantization of an electron wave vector in at least one dimension. , Ie, small, to indicate a quantum well, quantum wire or quantum dot superlattice, the Fermi level of the superconducting superlattice is tuned closer to the bottom of the subband of the superlattice, ie the Fermi The criticality of massive homogeneous superconductors (metal elements, alloys, metal compounds, doped semiconductors or oxides) by being tuned to what is called a "shape resonance" state for the electrons in the levels. It is based on the idea that the temperature Tc∞ can be increased. In the "shape resonance" state, the Fermi level is tuned to the maximum electronic density of states artificially created by confining electrons in the superconducting unit. A similar idea in a single quantum well (raising the critical temperature of superconductivity by confining the quantum, ie by tuning the Fermi level to a "shape resonance" state) has been reported by Brat and Thompson (JM Brat and CJ Thompson's Phys. Rev. Lett. 10.332 (1963); CJ Thompson and JM Brat's Phys. Lett. 5, 6 (1963)). , Which has been abandoned and forgotten by the scientific community because quantum fluctuations in the low dimension D ≦ 2 stress the superconducting phase in single quantum wells or quantum wires. The Applicant has increased the critical temperature Tc by realizing the "shape resonance" state in a "superlattice" of units rather than in a single superconducting unit and showing the effect of quantization by reduced size, He turned his research to showing that he could overcome problems. The applicant has used the ceramic superconductors of the family Bi2212 (perovskite of the formula _{Bi 2 Sr 2 Ca 1-x} Y x Cu 2 O 8 + copper oxide _y) to the experimental verification. In these oxides, it is known that the plane of Cu oxide is not homogeneous (edited by Y. Bur Yam et al., World Scientific Pub, Singapore, 1992, p. 65, A. Bianconi). “Lattice Effects in High-Tc Superconductors” by K. Mueller and G. Benedeck, World Scientific Pub, Singapore, 1992, No. 1 A. Bianconi, “Phase Separation in Cuprate Superconductors” on page 125), in particular, this material has domains with different values for the distance between the Cu atom and the apical oxygen. It is known that there is. The Applicant has planar copper oxide _{B i 2 Sr 2 CaCu 2 O} 8 + y at a temperature lower than 120K has demonstrated to have a modulated structure as shown in FIG. In this structure, there are multiple domains, that is, the bond between Cu and the apical oxygen is short (<2.4Å), and is formed by a lattice of distorted Cu site conformations having a constant period λ _p in the direction y. In some cases, stripes of width W called barriers are separated by stripes of width L in which the bonding between Cu and apical oxygen is long (> 2.5Å). The width L of the stripes is the ratio of the number of long copper-apex oxygen bonds to the total number of copper-apex oxygen bonds (1988, J. Willie and Sons Publishing, New York, R. Prinz and D. Conning). Measurement is performed using the EXAFS method described in “X Ray Absorption Principle, Applications Techniques of EXAFS, SEXAFS and XANES” ”edited by Sberger. That is, the period λ _{p in the} y direction is measured by electron diffraction, and the component of the wave vector (k _Fy ) of the electron at the Fermi level in the y direction is the angle-resolved light emission. (Based on J. Phys. Chem. Solid 53, 1583 (1992) by Z. X. Shen). Measurements carried out on single crystals grown by the "floating zone" method at Tc = 84 ° K show that the modulation period λ _p = 4.7a, where a = 5.4Å is the lattice constant, width L = 2.7a, and an electron wave vector component (k _Fy ) to 0.38 (± 0.03) 2π / a at the Fermi level was generated. The fringe width W, characterized by Cu sites with short Cu-apex oxygen bonds, was found to be 2a in the temperature range below 120K. The barrier width W = 10.8Å is about the superconducting Pippard coherence length ξ ₀ of the superconducting material. Experiments carried out in different superconductors with different doping levels and with different Y contents showed that the superstructure was changed by holding the Fermi level in a "shape resonance state" and L changed with doping. It was shown to do. The width W was assumed to be independent of doping. This is because it is related to the lattice instability at the critical doping δc = 1/8 of 1 hole / 8 Cu site (WE Pickett et al., Phys. Rev. Lett. 62, 2). 751 (1989)). Therefore, the electrons at the Fermi level in the stripe of width L are in the "shape resonance" state and are caught in the stripe of size L _defined by the barrier of size W, and the superlattice of period λ _p (Fig. 2)) and the Fermi level is tuned above the bottom of the m = 2 subband with wave vector k _Fy ˜2π / L. The “shape resonance” state can be defined in a more general way with reference to FIG. 3, in which the dashed line shows the curve of electronic density of states versus electron energy for a two-dimensional homogeneous conducting plane, and The solid line is the modified "density of states" vs. "energy" curve for the heterostructure shown in FIGS. Therefore, the density of states is modified by confining the electrons in a one-dimensional fringe superlattice as compared to a homogeneous material, which gives a new maximum for energy -Em, where m is the number of resonances. Values, and for the “shape resonance” state, as shown in FIG. 3, the Fermi level is in the range of the maximum value of the density of states / energy curve above the bottom of the sub-band Em generated by the heterostructure of the superconducting metal. Tuned quantum states are intended. According to the standard theory of superconductivity (BCS theory), the critical temperature Tc∞ for the transition from the ordinary metallic phase to the superconducting phase in an infinite homogeneous material is (1) Tc∞ ∼ ω _D exp (-1 / N ₀ V), and for a CuO ₂ superconducting plane, the Debye temperature has been found to be about 500 K, and the product N ₀ V has been found to be about 0.2, where N ₀ is the density of states at the Fermi level, and V is the electron-phonon coupling constant, so the critical temperature Tc∞ for the homogeneous CuO ₂ plane is in the range 7-15K. It is estimated that there is. In the heterogeneous CuO ₂ plane shown in FIG. 1, when the Fermi level is tuned to the m = 2 maximum of the density of states of the m = 2 subband of the quantum fringe superlattice, the density of states N at the Fermi energy is ₀ is increased and the critical temperature is increased. According to the solution of Thompson and Brat (CJ Thompson and JM Brat Phys. Lett. 5, 6 (1963)), the critical temperature for the quantum fringe superlattice can be written as it can. (2) Tc to ω _D exp (−1 / N ₀ V) exp {+ k / (N ₀ V)} where exp {+ k / (N ₀ V)} is an “amplification coefficient” determined by quantum confinement. A = Tc / Tc ∞ and k is related to the quantum confinement in the heterostructure for homogeneous materials and the effective increase in the density of states at the Fermi level by the shape resonance number m. In the case of a quantum fringe superlattice with the Fermi level tuned above the bottom of the m = 2 subband, the coefficient k is estimated to be 1/3, as seen in Bi2212, and therefore An amplification factor of about 5 is obtained. Critical temperature, in the superlattice is increased from a value that is normally expected in the case of CuO ₂ plane of the same type 7-15K to a high temperature range of 35-85K. From the above description, the Applicant has determined that the physical structure of the superconductor is arranged to follow the specific conditions identified for the Bi2212 copper oxide plane, and the structure of the new superconducting metallic material of high Tc is , Bi2212, which is determined to exist in this orderly non-homogeneous phase state, for example, it is possible to obtain superconductivity at a high critical temperature in an ordinary superconducting metal mainly used for niobium compounds. Reasoned. According to the present invention, a high critical temperature superconductor has a structure as shown in FIG. 2, that is to say that the superconductor 1 has a constant period λ _p in at least one direction (direction y in this case). A plurality of first portions 3 of superconducting material that form a lattice of substantially equal elements, and a plurality of first portions 3 that are not the same as the plurality of first portions 3 and that are arranged to separate the portions 3. Acting on the process of amplifying the critical temperature characteristic of the material shown pictorially at the level of the atomic plane formed by the metallic heterostructure made with the second part 4 and forming the homogenous part 3 in this heterostructure In order to do so, it is necessary that the above heterostructure realizes the quantum unit superlattice described for the copper oxide plane of FIG. This is obtained according to the invention by forming a part 3 having a size L as measured in the y direction and realizing a state of shape resonance for electrons of the Fermi level at wavelength λ _F , where This situation in the heterostructure described in Section 1 means that the size L must satisfy the following simple equation: (3) L ~ mλ _F / 2 Further, from the comparison between the theory of superconducting state in the superlattice and the heterostructure found in Bi2212, the second condition for realizing the present invention is that the part 4 is a superconducting quantum. It is presumed that, in order to stabilize the state, the superconducting material forming the portion 3 must have a size W of about the piper coherence length ξ ₀ . With respect to "moderate size", here and in the following description, since X has a range of 1 to 100, W has a value of ξ ₀ / x because of the Josephson coupling between the superconducting portions. It can not be said that. In the case of Bi2212, we have x˜1, but for large systems with ξ ₀ we can use x> 1 and reduce W. However, in any case, W must be large enough to reduce the probability of single particle hopping between superconducting portions and reduce the dispersion of the superlattice subbands. To elaborate on the realization of the heterostructure shown in FIG. 2, a superconductor with a high critical temperature is formed by a plurality of parallel atomic planes 2 and each plane 2 is a superconducting metallic material (in this definition A plurality of stripes 3 formed by a doped oxide as well), which have a width L equal to an integer half the wavelength of the electrons of the Fermi level in the stripe 3 according to equation (3) above. Furthermore, the plane 2 also comprises a plurality of second stripes 4 alternating with the stripes 3, which are substances with an electronic structure different from those forming the first stripes, It is formed of low metals or non-metals (non-metals also refer to substances such as organic compounds). Based on the above requirements, the fringe 4 has a width W of the order of the piped coherence length ξ ₀ of the superconducting material forming the fringe 3, and in order to stabilize the three-dimensional superconducting phase, It is also necessary to have adjacent parallel superconducting planes decorated with quantum fringe superlattices in the z-direction at a distance h of the order of the Pippard coherence length ξ ₀ . In the case of the superconductor 1 having the structure shown in FIG. 2, the formula (2) can be applied. Therefore, if the superconducting material forming the stripes 3 is known, an improved critical temperature is expected. In other words, in order to tune the Fermi level to a desired degree of shape resonance, the superconducting material forming the fringes 3 and the size of the superlattice component forming the heterostructure shown in FIG. By choice, a superconductor with the desired critical temperature can be realized "a priori". Large amplifications are obtained for small sizes of superconducting fringes that tune the Fermi level to shape resonances of low order m. Furthermore, the amplification factor of the heterostructure in equation (2) suppresses the action of the term exp (-1 / N ₀ V) in equation (1), which reduces the critical temperature and therefore a large ω _D. The amplification factor becomes more effective in the heterostructure formed by the superconducting material. FIG. 4 shows a superconductor 10 having a high critical temperature, which has a different structure than that shown in FIG. 2 but is constructed according to the parameters of the invention, and in particular , A plurality of first superconducting layers 11 are formed alternating with second layers 12 formed of a material that is not the same, the layers 11 having a selected thickness L, and the layers 12 Has a selected thickness W, tunes the Fermi level to the shape resonance state of the superlattice, and sets W ≦ ξ ₀ . FIG. 5 shows a third example of a superconductor 20 having a high critical temperature realized according to the present invention, which superconductor 20 comprises a plurality of wires 21 2 made of a superconducting material. Formed, they are parallel to one another and form a three-dimensional lattice, which is embedded in a matrix 22 formed of a material which is not the same as the line 21. The cross-sections of the lines, which are squares or circles, have a size L 1 selected to satisfy the selected shape resonance condition and are separated in the matrix 22 by a distance W 2. In general, the following equation can be used within the limits of negligible single particle hopping between fringes, layers or lines to determine the size L 1 that must satisfy the “shape resonance state” in the superlattice: . (4) k _F to (2π / L) (m / 2) where k _F is the wave vector of the electron at the Fermi level of the superconducting substance. More generally, the “shape resonance” state shown in FIG. 3 can be written as follows. (5) E _F ~ Em This means that the Fermi energy is tuned to artificial maximum of the electronic density of states, the state by the dispersion of the superlattice subband to non negligible hopping between the superconducting units ( Considering possible shifts in 4). Further, when the value of L obtained by using the equation (4) is small and it is difficult to realize the superconducting portion, the following equation can be used for the “shape resonance” state. . (6) | k _F −G | ~ (2π / L) (m / 2) where G is the reciprocal lattice vector of the superconducting material, and k _F is the wave vector of the electron in the Fermi level. Yes, and m is an integer. FIG. 6 is another example of a superconductor 30 having a high critical temperature realized by the present invention, in which the superconductor 30 is composed of a plurality of spherical particles made of a superconducting material forming a three-dimensional lattice 32. It is formed by the nuclei 31, which are embedded in a matrix 33 formed of a material that is not the same as the superconducting nuclei 31. The size of the nucleus is L, separated by W. Furthermore, FIG. 7 shows a superconductor 40 having a high critical temperature realized by the present invention as well as the superconductor 30, but the superconducting material is composed of a plurality of voids of size L forming a three-dimensional lattice. Spheres 41, which are embedded in a matrix 42 formed of a material that is not the same as the superconducting spheres 41, to provide a separation W between the spheres. Another option to realize a superconducting heterostructure with a high critical temperature according to the invention is to duplicate the structure of the superconducting plane of Bi2212 (FIG. 1), the material forming the second part 4 being at the level of the crystal lattice. Only in order to form a superlattice as shown in FIG. 2 which is different from the material forming the first part. Finally, a superconductor with a high critical temperature according to the present invention must satisfy the "shape resonance" condition where L is based on one of the given equations (4), (5) and (6). And must have one of the above structures where W is on the order of or less than the superconducting Pippard coherence length ξ ₀ . The superconducting materials described with respect to FIGS. 2, 4, 5, 6 and 7 can be realized by chemical reaction and / or doping of homogeneous materials, as in the case of the coupling, or the quantum lattice superlattice ( It can also be realized by making a heterostructure according to the invention as described below with respect to FIG. 8). That is, first, an atomically flat surface of a substrate 50 made of metal or non-metal is formed, and in a subsequent step, a plurality of superconducting units 51 are made of a superconducting material different from that of the substrate. Are obtained by molecular beam epitaxy or other equivalent techniques (eg sputtering, lithography, chemical synthesis, electrochemical deposition). The units 51 are arranged to realize a lattice of the same unit of size L forming a superlattice in at least one direction y, separated by a selected spacing W, to meet the above condition of "shape resonance" in the superlattice. Satisfactory, good lattice matching of the crystal planes of the different components is required to reduce the stress at the interface, and in the next step the material 52 is arranged to cover the substrate 50 and the superconducting unit 51, and finally The above two steps are repeated a fixed number of times to form the three-dimensional metal heterostructure 60. In the case of the superconductor 10 of FIG. 4, the method of forming an artificial superlattice of a superconducting layer having a thickness satisfying the “shape resonance” state (quantum well) is mainly based on molecular beam epitaxy or other methods. Comprising depositing layers 11 and 12 in an alternating manner by performing a certain number of equivalent techniques (eg sputtering, lithography, chemical synthesis, electrochemical deposition) to achieve a three-dimensional metal heterostructure 10. If this is the case, care must be taken to find substances 11 and 12 with a good crystal lattice match at the interface and to grow atomically flat surfaces. Industrial Applicability A metal heterostructure having a high critical temperature can be applied to manufacture of an electronic device using a superconducting material, and although only a few examples are shown here, its application is wide and SQ UID, Examples include Josephson junctions, infrared detectors, particle detectors, and high frequency filters.

[Procedure Amendment] Patent Law Article 184-8 [Date of submission] February 12, 1996 [Amendment] Description The field of invention of superconductors with a high Tc formed by a metal heterostructure at the atomic limit. , A high-critical-temperature superconductor according to the first part of the claim, which consists of an artificial heterostructure made of a first part of a superconducting material of size L pressed towards the atomic limit. Furthermore, the invention relates to a method for realizing these superconductors. DESCRIPTION OF THE PRIOR ART As is well known, commercially available superconducting metals exhibit only a very low critical temperature, which limits the industrial application of superconductivity. The onset temperature of zero, that is, the zero resistivity and the onset temperature of diamagnetism). These very low temperatures, on the order of a few degrees Kelvin, are unattainable without the use of cryogenic techniques, which means they are costly and difficult to operate. Therefore, research in this field is directed towards the realization of new superconducting materials with high critical temperatures. A recent innovation in this field is the discovery of superconductivity in cuprate perovskite, which exhibits a critical temperature on the order of 100 degrees Kelvin. However, ceramic superconductors of this type are fragile, difficult to shape, and difficult to keep oxygen content under control, which limits their industrial application. These challenges limit the industrial application of superconducting electronic devices using these ceramic materials. Another challenge to advances in this field is the lack of theory to explain superconductivity at high temperatures in these materials, and thus the inability to drive advances in these materials by experimental techniques. The superconducting cuprate perovskite has a c-axis direction in which a first superconducting CuO ₂ layer having a two-dimensional electronic structure is sandwiched by a second blocking layer made of a low Tc metal or an insulating material. Described as a natural superlattice, and a similar artificial superlattice has been synthesized (Physical Review Letters, Vol. 63, No. 9, August 1989, 1016-1019). Page, JM Toscon, MG Kirkut, L. Antognazza, O. Brunner, O. Fischer's "Y-Ba-Cu-O / Dy-Ba-Cu-O superlattice; "The first step towards the artificial construction of conductors"), as well as a recent patent application (Tray Industries European patent application EPA0502204A1, international application number PCT / IP91 /). 1255, International Publication No. WO 92/0514 (02.04.92 92/08); and some references (Physica C, Volume 190, ISSN 0921-4534, No. 1/2, December 1991, No. 22- . 2 page 6; Qi.Li.T Benkatesan and X.X.Xi: "YBa ₂ Cu ₃ O ₇ type superlattice growth and superconducting properties of"); (Physica C, the 185-1 Vol. 89, ISSN0921 -4534, 1, December 1991, pp. 1747-1748; M. Horcon, JP Koran, and WA Little: "A new in the close tunneling effect of high T c superconducting cuprates. have also been described phenomenon "). Moreover, the superconducting films of doped fullerene, such as K ₃ C ₆₀ (fullerene), the production of microelectronic devices that are complex laminated (Scientific Fook American (Internal Editing), October 1991, Volume 265, Issue 4, ISSN 0036-8733, pages 32-41, R. F. Curl and R. E. Smalley. the "fullerene (fullerenes)"). SUMMARY the present invention disclosed herein of the invention, physical for designing novel superconducting heterostructure several times than superconductors bulk metal having a large critical temperature The above problems are overcome by defining parameters According to the present invention, a plurality of superconducting materials forming a lattice of substantially equal elements having a constant period λ _p in at least a first direction y. Superconducting piper of superconducting material forming a plurality of first portions, the plurality of second portions being formed of a first portion separated by a second material having a different electronic structure. In a superconductor having a high critical temperature having a size W of the order of Pippard coherence length ξ ₀ (W ≦ ξ ₀ ), the plurality of first portions are measured in the first direction y. A supercritical superconductor having a size L and a period λ _p and having a charge density satisfying an electron “shape resonance” condition at a Fermi level is provided. The present invention is based on the discovery that high critical temperature superconductivity is associated with a particular heterostructure of a superconducting material, which heterostructure can be found in a cuprate perovskite. This dissimilar structure determines the "amplification degree" at the critical temperature compared to the same kind of superconducting material. Therefore, by forming an artificial dissimilar structure containing a superconducting metal with a low critical temperature, it is multiplied by the "amplification factor" associated with the selected heterostructure, and more so than with homogeneous materials. A superconductor having an artificially arranged dissimilar structure having a critical temperature several times higher or even 100 times higher is formed. The invention also relates to a method for realizing a superconducting heterostructure with a high critical temperature, based on the main claims characterized by: -Providing a substrate made of a metallic or non-metallic substance. Forming a plurality of first portions of superconducting material on the substrate, the first portions having a selected dimension L and a selected spacing W in at least the direction y; Forming on said first part a second part of a material having a different electronic structure which acts as a spacer. The spacing W must be of the order of the superconducting Pippard coherence length ξ ₀ of the superconducting material forming the plurality of first portions (W ≦ ξ ₀ ). Repeating the above forming steps a selected number of times until a three-dimensional heterostructure is realized. The dimension L and the spacing W are selected to achieve a "shape resonance" state for electrons in the Fermi level of superconducting metals. In particular, the heterostructure can be realized by molecular beam epitaxy. A second method, which is simpler to achieve a higher critical temperature superconductor according to the main claim, is that a plurality of films of superconducting material, i.e. the first part, are provided with a plurality of non-superconducting films (or critical films). A superconductor having a low temperature), that is, a three-dimensional heterostructure made of those separated by a second portion, wherein the thickness L of the superconducting film and the thickness W of the non-superconducting film are It relates to the formation of a three-dimensional heterostructure that realizes a "shape resonance" state for electrons at the Fermi level in the lattice. In order to realize the "shape resonance" state, the thickness of the superconducting metal film is about the thickness of a few atomic layers, and therefore the film thickness must be controlled to be uniform at the atomic limit. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows the structure of a CuO ₂ plane in _{Bi 2} Sr ₂ CaCu ₂ O ~8 decorated by stripes of different Cu site conformations is a square pyramid distorted defined by the applicant It is a figure. FIG. 2 is a superconducting heterostructure at the atomic limit formed by a quantum fringe superlattice realized in Bi ₂ Sr ₂ CaCu ₂ O _.about.8 , which has a critical superconducting temperature of about 10 according to the present invention. It is a figure which shows the structure which gives the amplification of 1st Embodiment of this invention. FIG. 3 is a diagram showing the low-quality behavior of the quantum fringe superlattice in the CuO ₂ plane, in which the Fermi energy is tuned to the maximum value of the state density in order to raise the critical temperature. Is. 4 to 7 are diagrams showing some types of superconducting heterostructures at the atomic limit formed by superlattices of quantum wells, quantum wires, quantum dots, and quantum spheres, respectively, as other embodiments of the present invention. . FIG. 8 is a diagram showing, as an example, a method of forming a superlattice of quantum wires. BEST MODE FOR CARRYING OUT THE INVENTION The present invention shapes a superconducting material into a plurality of units forming a superlattice, the size L of each unit being a function of the quantization of an electron wave vector in at least one dimension. , Ie, small, to indicate a quantum well, quantum wire or quantum dot superlattice, the Fermi level of the superconducting superlattice is tuned closer to the bottom of the subband of the superlattice, ie the Fermi The criticality of massive homogeneous superconductors (metal elements, alloys, metal compounds, doped semiconductors or oxides) by being tuned to what is called a "shape resonance" state for the electrons in the levels. It is based on the idea that the temperature Tc∞ can be increased. In the "shape resonance" state, the Fermi level is tuned to the maximum electronic density of states artificially created by confining electrons in the superconducting unit. A similar idea in a single quantum well (raising the critical temperature of superconductivity by confining the quantum, ie by tuning the Fermi level to a "shape resonance" state) has been reported by Brat and Thompson (JM Brat and CJ Thompson's Phys. Rev. Lett. 10.332 (1963); CJ Thompson and JM Brat's Phys. Lett. 5, 6 (1963)). , Which has been abandoned and forgotten by the scientific community because quantum fluctuations in the low dimension D ≦ 2 stress the superconducting phase in single quantum wells or quantum wires. The Applicant has increased the critical temperature Tc by realizing the "shape resonance" state in a "superlattice" of units rather than in a single superconducting unit and showing the effect of quantization by reduced size, He turned his research to showing that he could overcome problems. The applicant has used the ceramic superconductors of the family Bi2212 (perovskite of the formula _{Bi 2 Sr 2 Ca 1-x} Y x Cu 2 O 8 + copper oxide _y) to the experimental verification. In these oxides, it is known that the plane of Cu oxide is not homogeneous (edited by Y. Bur Yam et al., World Scientific Pub, Singapore, 1992, p. 65, A. Bianconi). "Lattice Effects in High-Tc Superconductors" by K. Mueller and G. Benedeck, World Scientific Pub, Singapore, 1992. A. Bianconi, page 125, "Phase Separation in Cuprate Superconductors," in particular, this material has different values for the distance between the Cu atom and the apical oxygen. It is known that there is a domain. Applicants have demonstrated that the Bi ₂ Sr ₂ CaCu ₂ O _{8 + y} copper oxide planes at temperatures below 120 K have a modulated structure as shown in FIG. In this structure, there are multiple domains, that is, the bond between Cu and the apical oxygen is short (<2.4Å) and is formed by a lattice of distorted Cu site conformations with a constant period λ _p in the direction y. Also, there are stripes with a width W, which are called barriers, separated by stripes with a width L in which the bond between Cu and apical oxygen is long (> 2.5Å). The width L of the stripes is the ratio of the number of long copper-apex oxygen bonds to the total number of copper-apex oxygen bonds (1988, J. Willie and Sons Publishing, New York, R. Prinz and D. Conning). Measurement is performed using the EXAFS method described in “X Ray Absorption Principle, Applications Techniques of EXAFS, SEXAFS and XANES” ”edited by Sberger. That is, the period λ _{p in the} y direction is measured by electron diffraction, and the component of the wave vector (k _Fy ) of the electron at the Fermi level in the y direction is the angle-resolved light emission. (Based on J. Phys. Chem. Solid 53, 1583 (1992) by Z. X. Shen). Measurements carried out on single crystals grown by the "floating zone" method at Tc = 84 ° K show that the modulation period λ _p = 4.7a, where a = 5.4Å is the lattice constant, width L = 2.7a, and an electron wave vector component (k _Fy ) to 0.38 (± 0.03) 2π / a at the Fermi level was generated. The fringe width W, characterized by Cu sites with short Cu-apex oxygen bonds, was found to be 2a in the temperature range below 120K. The barrier width W = 10.8Å is about the superconducting Pippard coherence length ξ ₀ of the superconducting material. Experiments carried out in different superconductors with different doping levels and with different Y contents showed that the superstructure was changed by holding the Fermi level in a "shape resonance state" and L changed with doping. It was shown to do. The width W was assumed to be independent of doping. This is because it is related to the lattice instability at the critical doping δc = 1/8 of 1 hole / 8 Cu site (WE Pickett et al., Phys. Rev. Lett. 62, 2). 751 (1989)). Therefore, the electrons at the Fermi level in the stripe of width L are in the "shape resonance" state and are caught in the stripe of size L _defined by the barrier of size W, and the superlattice of period λ _p (Fig. 2)) and the Fermi level is tuned above the bottom of the m = 2 subband with wave vector k _Fy ˜2π / L. The “shape resonance” state can be defined in a more general way with reference to FIG. 3, in which the dashed line shows the curve of electronic density of states versus electron energy for a two-dimensional homogeneous conducting plane, and The solid line is the modified "density of states" vs. "energy" curve for the heterostructure shown in FIGS. Therefore, the density of states is modified by confining the electrons in a one-dimensional fringe superlattice compared to homogeneous materials, which gives a new maximum for the energy Em, where m is the number of resonances. For the “shape resonance” state, as shown in FIG. 3, the Fermi level is in the range of the maximum value of the density of states / energy curve above the bottom of the sub-band Em generated by the heterostructure of the superconducting metal. A tuned quantum state is intended. According to the standard theory of superconductivity (BCS theory), the critical temperature Tc∞ for the transition from the ordinary metallic phase to the superconducting phase in an infinite homogeneous material is (1) Tc∞ ∼ ω _D exp (-1 / N ₀ V), and for a CuO ₂ superconducting plane, the Debye temperature has been found to be about 500 K, and the product N ₀ V has been found to be about 0.2, where N ₀ is the density of states at the Fermi level, and V is the electron-phonon coupling constant, so the critical temperature Tc∞ for the homogeneous CuO ₂ plane is in the range 7-15K. It is estimated that there is. In the heterogeneous CuO ₂ plane shown in FIG. 1, when the Fermi level is tuned to the m = 2 maximum of the density of states of the m = 2 subband of the quantum fringe superlattice, the density of states N at the Fermi energy is ₀ is increased and the critical temperature is increased. According to the solution of Thompson and Brat (CJ Thompson and JM Brat Phys. Lett. 5, 6 (1963)), the critical temperature for the quantum fringe superlattice can be written as it can. (2) Tc to ω _D exp (−1 / N ₀ V) exp {+ k / (N ₀ V)} where exp {+ k / (N ₀ V)} is an “amplification coefficient” determined by quantum confinement. A = Tc / Tc ∞ and k is related to the quantum confinement in the heterostructure for homogeneous materials and the effective increase in the density of states at the Fermi level by the shape resonance number m. In the case of a quantum fringe superlattice with the Fermi level tuned above the bottom of the m = 2 subband, an amplification factor A 2 of about 15 is obtained, as seen in Bi2212. Critical temperature, in the superlattice is increased from a value that is normally expected in the case of CuO ₂ plane of the same type 7-15K to a high temperature range of 60-150K. From the above description, the Applicant has determined that the physical structure of the superconductor is arranged to follow the specific conditions identified for the Bi2212 copper oxide plane, and the structure of the new superconducting metallic material of high Tc is , Bi2212, which is determined to exist in this orderly non-homogeneous phase state, for example, it is possible to obtain superconductivity at a high critical temperature in an ordinary superconducting metal mainly used for niobium compounds. Reasoned. According to the present invention, a high critical temperature superconductor has a structure as shown in FIG. 2, that is to say that the superconductor 1 has a constant period λ _p in at least one direction (direction y in this case). A plurality of first portions 3 of superconducting material that form a lattice of substantially equal elements, and a plurality of first portions 3 that are not the same as the plurality of first portions 3 and that are arranged to separate the portions 3. Acting on the process of amplifying the critical temperature characteristic of the material shown pictorially at the level of the atomic plane formed by the metallic heterostructure made with the second part 4 and forming the homogenous part 3 in this heterostructure In order to do so, it is necessary that the above heterostructure realizes the quantum unit superlattice described for the copper oxide plane of FIG. This is obtained according to the invention by forming a part 3 having a size L as measured in the y direction and realizing a state of shape resonance for electrons of the Fermi level at wavelength λ _F , where This situation in the heterostructure described in Section 1 means that the size L must satisfy the following simple equation: (3) L ~ mλ _F / 2 Further, from the comparison between the theory of superconducting state in the superlattice and the heterostructure found in Bi2212, the second condition for realizing the present invention is that the part 4 is a superconducting quantum. It is presumed that, in order to stabilize the state, the superconducting material forming the portion 3 must have a size W of about the piper coherence length ξ ₀ . With respect to "moderate size", here and in the following description, since x has a range of 1 to 100, the value of W must be ξ ₀ / x because of the Josephson coupling between the superconducting portions. It can not be said that. In the case of Bi2212, we have x˜1, but for large systems with ξ ₀ we can use X> 1 and reduce W. However, in any case, W must be large enough to reduce the probability of single particle hopping between superconducting portions and reduce the dispersion of the superlattice subbands. To elaborate on the realization of the heterostructure shown in FIG. 2, a superconductor with a high critical temperature is formed by a plurality of parallel atomic planes 2 and each plane 2 is a superconducting metallic material (in this definition A plurality of stripes 3 formed by a doped oxide or a semiconductor), which have a width L equal to an integer half the wavelength of the electrons of the Fermi level in the stripes 3 according to the above equation (3). Have. Furthermore, the plane 2 also comprises a plurality of second stripes 4 alternating with the stripes 3, which are substances with an electronic structure different from those forming the first stripes, It is formed of a low metal or non-metal or vacuum (non-metal also refers to materials such as organic compounds). Based on the above requirements, the stripes 4 have a width W of the order of the piped coherence length ξ ₀ of the superconducting material forming the stripes 3. Furthermore, in order to stabilize the three-dimensional superconducting phase, It is also necessary to have adjacent parallel superconducting planes decorated with quantum fringe superlattices in the z-direction at a distance h of the order of the Padcoherence length ξ ₀ . In the case of the superconductor 1 having the structure shown in FIG. 2, the formula (2) can be applied. Therefore, if the superconducting material forming the stripes 3 is known, an improved critical temperature is expected. In other words, in order to tune the Fermi level to a desired degree of shape resonance, the superconducting material forming the fringes 3 and the size of the superlattice component forming the heterostructure shown in FIG. By choice, a superconductor with the desired critical temperature can be realized "a priori". Large amplifications are obtained for small sizes of superconducting fringes that tune the Fermi level to shape resonances of low order m. Furthermore, the amplification factor of the heterostructure in equation (2) suppresses the action of the term exp (-1 / N ₀ V) in equation (1), which reduces the critical temperature and therefore a large ω _D. The amplification factor becomes more effective in the heterostructure formed by the superconducting material. FIG. 4 shows a superconductor 10 having a high critical temperature, which has a different structure than that shown in FIG. 2 but is constructed according to the parameters of the invention, and in particular , A plurality of first superconducting layers 11 are formed alternating with second layers 12 formed of a material that is not the same, the layers 11 having a selected thickness L, and the layers 12 Has a selected thickness W, tunes the Fermi level to the shape resonance state of the superlattice, and sets W ≦ ξ ₀ . FIG. 5 shows a third example of a superconductor 20 having a high critical temperature realized according to the present invention, which superconductor 20 comprises a plurality of wires 21 2 made of a superconducting material. Formed, they are parallel to one another and form a three-dimensional lattice, which is embedded in a matrix 22 formed of a material which is not the same as the line 21. The cross-sections of the lines, which are squares or circles, have a size L 1 selected to satisfy the selected shape resonance condition and are separated in the matrix 22 by a distance W 2. In general, the following equation can be used within the limits of negligible single particle hopping between fringes, layers or lines to determine the size L 1 that must satisfy the “shape resonance state” in the superlattice: . (4) k _F to (2π / L) (m / 2) where k _F is the wave vector of the electron at the Fermi level of the superconducting substance. More generally, the “shape resonance” state shown in FIG. 3 can be written as follows. (5) E _F ~ Em This means that the Fermi energy is tuned to artificial maximum of the electronic density of states, the state by the dispersion of the superlattice subband to non negligible hopping between the superconducting units ( Considering possible shifts in 4). Further, when the value of L obtained by using the equation (4) is small and it is difficult to realize the superconducting portion, the following equation can be used for the “shape resonance” state. . (6) | k _F −G | ~ (2π / L) (m / 2) where G is the reciprocal lattice vector of the superconducting material, and k _F is the wave vector of the electron in the Fermi level. Yes, and m is an integer. FIG. 6 is another example of a superconductor 30 having a high critical temperature realized by the present invention, in which the superconductor 30 is composed of a plurality of spherical particles made of a superconducting material forming a three-dimensional lattice 32. It is formed by the nuclei 31, which are embedded in a matrix 33 formed of a material that is not the same as the superconducting nuclei 31. The size of the nucleus is L, separated by W. Furthermore, FIG. 7 shows a superconductor 40 having a high critical temperature realized by the present invention as well as the superconductor 30, but the superconducting material is composed of a plurality of voids of size L forming a three-dimensional lattice. Spheres 41, which are embedded in a matrix 42 formed of a material that is not the same as the superconducting spheres 41, to provide a separation W between the spheres. Another option to realize a superconducting heterostructure with a high critical temperature according to the invention is to duplicate the structure of the superconducting plane of Bi2212 (FIG. 1), the material forming the second part 4 being at the level of the crystal lattice. Only in order to form a superlattice as shown in FIG. 2 which is different from the material forming the first part. Finally, a superconductor with a high critical temperature according to the present invention must satisfy the "shape resonance" condition where L is based on one of the given equations (4), (5) and (6). And must have one of the above structures where W is on the order of or less than the superconducting Pippard coherence length ξ ₀ . The superconducting materials described with respect to FIGS. 2, 4, 5, 6 and 7 can be realized by chemical reaction and / or doping of complex materials, as in the case of couplings, or superlattices of quantum wires ( It can also be realized by making a heterostructure according to the invention as described below with respect to FIG. 8). That is, first, an atomically flat surface of a substrate 50 made of metal or non-metal is formed, and in a subsequent step, a plurality of superconducting units 51 are made of a superconducting material different from that of the substrate. Are obtained by molecular beam epitaxy or other equivalent techniques (eg sputtering, lithography, chemical synthesis, electrochemical deposition). The units 51 are arranged to realize a lattice of the same unit of size L forming a superlattice in at least one direction y, separated by a selected spacing W, to meet the above condition of "shape resonance" in the superlattice. Satisfactory, good lattice matching of the crystal planes of the different components is required to reduce the stress at the interface, and in the next step the material 52 is arranged to cover the substrate 50 and the superconducting unit 51, and finally The above two steps are repeated a fixed number of times to form the three-dimensional metal heterostructure 60. In the case of the superconductor 10 of FIG. 4, the method of forming an artificial superlattice of a superconducting layer having a thickness satisfying the “shape resonance” state (quantum well) is mainly based on molecular beam epitaxy or other methods. Comprising depositing layers 11 and 12 in an alternating manner by performing a certain number of equivalent techniques (eg sputtering, lithography, chemical synthesis, electrochemical deposition) to achieve a three-dimensional metal heterostructure 10. If this is the case, care must be taken to find substances 11 and 12 with a good crystal lattice match at the interface and to grow atomically flat surfaces. Industrial Applicability Metal heterostructures with high critical temperature can be applied to the manufacture of electronic devices using superconducting materials, and only a few examples are shown here, but their applications are wide and they are widely used. Examples of magnetic systems include SQUIDs, Josephson junctions, infrared detectors, particle detectors, and high frequency filters. Claims 1. A plurality of first parts (3, 11, 21, 31, 41) made of a first superconducting material and different electrons inserted in these first parts so as to realize a separation between the first parts. A first part formed by an artificial heterostructure made of a plurality of second parts (4, 12, 22, 32, 42) made of a structured second material and combined with the second part The artificial unit of is repeated at least a selected number of times until a superlattice having a period λ _p in at least a first direction (y) is realized, and the plurality of second portions (4, 12, 22, 32, 42) Is a critical temperature at which the size W measured in the direction (y) has a size W that is about the superconducting piped coherence length ξ ₀ of the superconducting material forming the first portion or less. Measurement in the above direction (y) for high-conductivity superconductors The size L and / or the charge density of the plurality of first portions (3, 11, 21, 31, 41) satisfy the “shape resonance” condition for electrons of the Fermi level, and the Fermi energy is the superlattice. A high critical temperature superconductor characterized in that it is tuned near the energy at the bottom or top of the sub-band. 2. A plurality of first portions formed of a first layer (11) made of a first superconducting material, a plurality of first portions made of a second layer (12) made of a second material having different electronic structures. Formed by alternating two parts, the first part being formed by a first layer (11) having a thickness L and the second part being formed by a second layer (12) having a thickness W. The superconductor having a high critical temperature according to claim 1, wherein the Fermi level is tuned to the "shape resonance" of the superlattice. 3. Formed by a plurality of parallel atomic planes (2) separated by a distance (h) in a direction (z), each plane extending in a direction (x) having a width (L) measured in the direction (y). A plurality of first portions formed by first stripes (3) made of a first superconducting material and a second material alternating with the first stripes (3) and having a different electronic structure. An artificial unit of first stripes formed by a plurality of second parts formed by the second stripes (4) made of and combined with the second stripes is periodic in the direction (y). λ _p , the plurality of first fringes (3) have a width L satisfying a “shape resonance” condition for Fermi level electrons, and the plurality of second fringes (4) are has a superconducting pin par de coherence length xi] ₀ degree or smaller width W of the superconducting material forming the first portion, and the plurality Plane, superconducting Pi par de coherence length ξ distance h of the order of ₀ high critical temperature according to claim 1, which is separated superconductor of the superconducting material forming the stripes (3) of the superconducting. 4. A plurality of parallel superconducting wires (21) forming a three-dimensional lattice, the superconducting wires being embedded in a matrix (22) made of a second material having a different electronic structure, Line (21) has a cross section of size (L) so as to satisfy the “shape resonance” condition for electrons of the Fermi level, and the superconducting material forming the superconducting wire (21) is The superconductor having a high critical temperature according to claim 1, wherein the superconductors are separated by a distance (W) of the order of the superconducting piped coherence length ξ ₀ or less. 5. Formed by a plurality of substantially spherical nuclei (31) formed of superconducting material separated by a distance (W) from each other to form a three-dimensional lattice embedded in a matrix (32), The nucleus (31) has a cross section of size (L) so as to satisfy the “shape resonance” condition for electrons of the Fermi level, and the superconducting substance of the superconducting material forming the superconducting nucleus (31) is superposed. The superconductor having a high critical temperature according to claim 1, wherein the superconductors have a high critical temperature and are separated by a distance (W) that is equal to or smaller than the conduction piped coherence length ξ ₀ . 6. Fullerenes formed by a plurality of empty spheres (41) formed of a superconducting material and separated from each other by a distance (W) form a three-dimensional lattice embedded in a matrix (42). The plurality of empty spheres (41) have a cross section of size (L) so as to satisfy the “shape resonance” condition with respect to electrons of the Fermi level, and the superconducting piped of a superconducting material. The superconductor having a high critical temperature according to claim 1, wherein the superconductors are separated by a distance (W) that is equal to or smaller than the coherence length ξ ₀ . 7. A superconducting first part superlattice according to any of the above claims and a second part, wherein the first and second parts are in terms of their crystal lattice, the substitution of atoms or the concentration of chemical dopants. The superconductor having a high critical temperature according to claim 1, which is different only. 8. The method for realizing a superconducting heterostructure having a high critical temperature according to claim 1, wherein the surface of a substrate made of a metallic or non-metallic material is adjusted and required for lattice matching and / or surface smoothing. If so, attach a buffering agent to form a first superconducting portion of size L controlled at the atomic level, to form a second portion that acts as a spacer for separating the first portion by a distance W, This is done by forming a well defined domain wall at the atomic level between the first and second parts and repeating the above steps a number of times established to achieve a three dimensional superlattice, The size L and the separation W of the first part are such that the Fermi level is tuned to the "shape resonance" state of the superlattice of the superconducting part, and the spacing W is the superconducting piped coherence length ξ _{0 of the} superconducting material. Degree or less Method characterized in that there. 9. The method for realizing a superconducting heterostructure having a high critical temperature according to claim 8, wherein the heterostructure is obtained by using a molecular beam epitaxy method. Ten. A three-dimensional heterostructure formed by alternating parallel layers of a superconducting layer (first portion) and a non-superconducting layer (second portion) according to claim 1, a molecular beam epitaxy or other equivalent technique, Use two materials with good crystal lattice matching at the interface, for example by sputtering, lithography, chemical synthesis, electrochemical deposition, and control the growth of atomically flat interfaces in layers of selected thickness 9. The method for realizing a superconductor having a high critical temperature according to claim 8, wherein the superconductor of the superconducting unit is formed by obtaining a "shape resonance" state.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Internal reference number FI C30B 29/22 501 7202-4G C30B 29/22 501Z H01L 39/02 8832-4M H01L 39/02 D (81) Designated countries EP (AT, BE, CH, DE, DK, ES, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE), OA (BF, BJ, CF, CG, CI, CM, GA, GN, ML, MR, NE, SN, TD, TG), AP (KE, MW, SD, SZ), AM, AT, AU, BB, BG, BR, BY, CA, CH, CN , CZ, DE, DK, ES, FI, GB, GE, HU, JP, KE, KG, KP, KR, KZ, LK, LT, LU, LV, MD, MG, MN MW, NL, NO, N Z, PL, PT, RO, RU, SD, SE, SI, SK, TJ, TT, UA, US, UZ, VN

Claims (1)

[Claims] 1. A plurality of first portions (3, 11, 21, 31, 41) of superconducting material forming a lattice of substantially equal elements having a constant period λ _p in at least a first direction (y), and these first portions Formed by a heterostructure made up of a plurality of second parts (4, 12, 22, 32, 42) made of non-identical material inserted into these first parts so as to achieve separation between , The plurality of first portions (3, 11, 21, 31, 41) have a size L and a period λ _p measured in the direction (y), and for electrons of the Fermi level The condition of the shape resonance condition is satisfied, and the plurality of second portions (4, 12, 22, 32, 42) have a superconducting piped coherence length ξ ₀ of the superconducting material forming the first portion. High critical temperature characterized by having a size W of a degree or less Superconductor. 2. A plurality of first layers (11) are formed alternating with second layers (12), the first layer (11) or first portion having a thickness L, and the second layer (12). ), That is, the second portion has a thickness W for tuning the Fermi level to shape resonance. 3. It is formed by a plurality of parallel atomic planes (2) separated by a distance (h) in the direction (z), and each plane has a direction (y ) A plurality of stripes (3) of superconducting material extending in a direction (x) having a width (L) and a period (λ _p ) as measured at) and a material which is alternating with this first stripe and which is not the same. And a plurality of second stripes (4) formed by the plurality of second stripes (4), the plurality of second stripes (4) having a superconducting piped coherence length ξ ₀ of the superconducting material forming the first portion. Having a size W of a degree or less, and the planes are separated by a distance h of a degree of the superconducting pippard coherence length ξ ₀ of the superconducting material forming the superconducting fringes (3). The superconductor having a high critical temperature according to claim 1. 4. A plurality of parallel superconducting wires (21) forming a three-dimensional lattice, the superconducting wires being embedded in a matrix (22) formed of a material which is not the same as the superconducting wires (21). ) Has a size (L) section that is an integral multiple of half the wavelength of electrons in the Fermi level in order to realize a shape resonance state, and is a superconducting material superconducting material that forms the superconducting wire (21). The superconductor having a high critical temperature according to claim 1, wherein the superconductors have a high critical temperature and are separated by a distance (W) that is equal to or smaller than the conduction piped coherence length ξ ₀ . 5. Formed by a plurality of substantially spherical nuclei (31) formed of superconducting material separated by a distance (W) from each other to form a three-dimensional lattice embedded in a matrix (32), The nucleus (31) has a size (L) section that is an integral multiple of half the wavelength of electrons in the Fermi level in order to realize a shape resonance state, and the superconducting nucleus (31) is formed. The superconductor having a high critical temperature according to claim 1, wherein the superconductors are separated by a distance (W) that is equal to or less than the superconducting piped coherence length ξ ₀ of the substance. 6. Fullerenes formed by a plurality of empty spheres (41) formed of superconducting material, separated for example by a distance (W) from each other, form a three-dimensional lattice embedded in a matrix (42). , The plurality of empty spheres (41) have a size (L) section to realize a shape resonance state, and the distance is less than or equal to the superconducting Pippard coherence length ξ ₀ of the superconducting material. The superconductor having a high critical temperature according to claim 1, which is separated only by (W). 7. Realized by a superlattice of a superconducting first part according to any of the preceding claims, the second part forming the first part only for different crystal lattices, different compositions or different concentrations of chemical dopants. The superconductor having a high critical temperature according to claim 1, which is formed of a material different from the above. 8. In a method of achieving a superconducting heterostructure with a high critical temperature, a surface of a substrate made of a metal or non-metal material is prepared, and a buffer is added if necessary for lattice matching and / or surface smoothing. Forming a first superconducting portion of the size L which is attached at an atomic level and forms a second portion which acts as a spacer for separating the first portion by a distance W, which is the first portion And a second part are formed by forming a domain wall well defined at the atomic level, and the above steps are repeated as many times as is established to realize a three-dimensional superlattice, and the size L of the first part is And the separation W is characterized in that the Fermi level is tuned to the "shape resonance" state of the superlattice of the superconducting part. 9. A method for realizing a superconducting heterostructure having a high critical temperature, which comprises obtaining the above heterostructure by using a molecular beam epitaxy method. Ten. A superconductor having a high critical temperature characterized by a three-dimensional heterostructure formed by alternating parallel layers of a superconducting layer (first portion) and a non-superconducting layer (second portion) according to claim 1. , Molecular beam epitaxy or other equivalent techniques such as sputtering, lithography, chemical synthesis, electrochemical deposition, using two materials with good crystal lattice matching at the interface, and layers of selected thickness This method is realized by controlling the growth of a flat interface at the atomic level and obtaining a "shape resonance" state in the superlattice of the superconducting unit.